A valve is commonly used to control the flow of a fluid between an input and an output. Specialized valves, known as mixing valves, have been developed to allow the combination of two inputs. Mixing valves can also control the volumetric flow from the inputs. Mixing valves are typically used in a water system to mix hot and cold water. For example, mixing valves are commonly found in bathrooms and kitchens, where they allow the user to produce varying degrees of warm water.
One mixing valve is particularly widespread in the marketplace. The model 963 mixing valve by the Mixet Co., a division of Alsons Corp, of Pico Rivera, Calif. has been placed in millions of apartments and homes throughout the United States. FIG. 4 provides a sectional view of the Model 963 valve designated by reference numeral 10. The valve 10 comprises a valve cartridge threaded within the valve body 11. The valve body has a first input 12 and a second input 14. Each input is connected to an output 18 by a passage formed within the valve body 11. Conduits 12a, 12b connect input 12 to mixing area 16. Conduits 14a and 14b connect input 14 to mixing area 16. The mixed water then enters output 18. Many times the output 18 can be directed to either a shower head or a bath tub faucet.
In use, the cartridge can be advanced or retreated within the valve body 11 by a handle attached to connection 22. When fully advanced, the cartridge 20 blocks the flow of water. A gasket 28 is attached to the cartridge by screw 30. However, the cartridge head 26 has a radial surface of diminished diameter. Thus, when the cartridge is retreated away from the mixing area, as shown, the diminished area opens a path between the inputs 12 and 14 and the output 18. An 0-ring 24 prevents leakage between the cartridge 20 and the valve body 11.
The Mixet Model 963 displays a serious problem caused by the design of its valve cartridge 20. The cartridge fails to adequately seal the space between wall 13 and cartridge head 26. Due to the diminished radial diameter of a portion of the head 26, very little material separates the pressurized water in conduit 12a and conduit 14a. Therefore, water will erode a pathway between the head portion 26 and the wall 13 adjacent to conduits 12b and 14b. Once eroded, water from one supply "bleeds" into the other supply. For example, if the hot water supply is at a higher pressure than the cold water supply, the hot water will displace cold water in the cold water input lines. This can produce severe and unwanted results. For example, a person using a sink with an eroded valve structure could easily scald themselves with hot water when expecting cold water. This problem is severe enough that city inspectors can close an apartment complex down to force the owners to replace the faulty valves. Replacement is an expensive procedure. The wall around the valve must be destroyed and the valve removed, at a cost of hundreds of dollars.
A need exists for a valve cartridge that can easily replace the existing valve cartridge to prevent such erosion. Such a valve should also be suitable for placement into an eroded valve structure where it can seal the eroded portion.